logo

CuriousTab

CuriousTab

Discussion

Home ‣ Electronics and Communication Engineering ‣ Microwave Communication See What Others Are Saying!
  • Question

  • Assertion (A): A backward wave oscillator has an internal positive feedback.

    Reason (R): A positive feedback is necessary for sustained oscillations.


  • Options
  • A. Both A and R are correct and R is correct explanation of A
  • B. Both A and R are correct but R is not correct explanation of A
  • C. A is correct but R is wrong
  • D. A is wrong but R is correct

  • Correct Answer
  • Both A and R are correct but R is not correct explanation of A 

    Explanation
    It is somewhat similar to TWT and can deliver microwave power over a wide frequency band.

    It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT.

    The growing RF wave travels in opposite direction to the electron beam.

    The frequency of wave can be changed by changing the voltage which controls the beam velocity.

    Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current.

    It features are:

    1. Frequency range - 1 GHz to 1000 GHz.

    2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed).

    It is used as signal source in transmitters and instruments.

    More questions

    • 1. A class A chopper has an input voltage of 200 V. Ton = 1.5 ms and Toff = 4.5 ms. The duty cycle, average output voltage and ripple factor respectively are

    • Options
    • A. 0.5, 100 V and 1
    • B. 0.25, 50 V and 3
    • C. 0.25, 50 V and 1
    • D. 0.5, 100 V and 3
      • Discuss
    • 2. The velocity factor of a transmission line depends on

    • Options
    • A. temperature
    • B. skin effect
    • C. relative permittivity of dielectric
    • D. none of the above
      • Discuss
    • 3. For node 1 in figure, KCL equation is

    • Options
    • A.
    • B.
    • C.
    • D. none of the above
      • Discuss
    • 4. Maxterm designation for A + B + C is

    • Options
    • A. M0
    • B. M1
    • C. M3
    • D. M4
      • Discuss
    • 5. Expression ++i is equivalent to

    • Options
    • A. i = i + 2
    • B. i = i + 1
    • C. i = i - 1
    • D. i = i + i + i
      • Discuss
    • 6. An LVDT is used to measure displacement. The LVDT feeds a Voltmeter of 0-5 V range through a 250 gain amplifier. For a displacement 0.5 mm the output of LVDT is 2 mV. The sensitivity of instrument is

    • Options
    • A. 0.1 V/mm
    • B. 0.5 V/mm
    • C. 1 V/mm
    • D. 5 V/mm
      • Discuss
    • 7. Consider the following statement: In case of a superconductor

      1. B = 0
      2. ?r is high
      3. diamagnetism is high
      4. transition temperature varies with isotopic mass.
      Of the above statements

    • Options
    • A. 1 and 2 are correct
    • B. 2, 3, 4 are correct
    • C. 1, 3, 4 are correct
    • D. 2, 4 are correct
      • Discuss
    • 8. An electron (charge -e) is rotating in a circular orbit of radius R, around a proton with charge +e at a constant angular velocity ?. The orbital magnetic dipole moment is

    • Options
    • A. 0.5 e? R2
    • B. e? R2
    • C. 2 e? R2
    • D. 0.5 e? R3
      • Discuss
    • 9. For a given value (n) of principle quantum number, the number of possible electronic states are

    • Options
    • A. n
    • B. n2
    • C. n3
    • D. n
      • Discuss
    • 10. A dielectric of relative permittivity ?r is subjected to a homogeneous electric field E. The dipole moment P per unit volume is given by

    • Options
    • A. P = constant
    • B. P = ?0 E
    • C. P = ?0(?r - 1) E
    • D. P = ?r E
      • Discuss

    Comments

    There are no comments.
Enter a new Comment




Aptitude

Engineering

Programming

Reasoning

Links

Copyright ©CuriousTab. All rights reserved.